1. Field of the Invention
The present invention relates to a substrate processing apparatus for processing a substrate such as a semiconductor substrate, and more particularly to a substrate processing apparatus for processing a semiconductor substrate for formation of a thin film, polishing, or the like in a chamber evacuated by a vacuum pump.
2. Description of the Related Art
Generally, when a substrate is processed at a pressure lower than the atmospheric pressure (hereinafter referred to as xe2x80x9cvacuumxe2x80x9d), the substrate is introduced into a vacuum chamber evacuated by a vacuum pump, and a process, such as formation of a thin film, plating, or polishing, is then carried out in the vacuum chamber. Various methods are known for forming a thin film on the surface of a substrate. These methods include physical vapor deposition (PVD) such as sputtering and ion plating, and chemical vapor deposition (CVD) utilizing vacuum evaporation or thermal reaction or plasma excitation under a low pressure. In addition to the thin film deposition, various other methods of processing a substrate at a low pressure, such as surface processing with dry etching, pattern exposure, resist processing, cleaning, drying, annealing, ion implantation, inspection, and measurement.
FIG. 5 is a schematic view showing an example of the whole structure of a conventional substrate processing apparatus, which is a film deposition apparatus for forming a thin film of a high dielectric material or a ferroelectric material, such as barium titanate, strontium titanate, or the like, through the CVD process. As shown in FIG. 5, in this substrate processing apparatus (film deposition apparatus), a hermetically sealed vacuum chamber (deposition chamber) 110 is provided downstream of a vaporizer (a gas generator) 100 for vaporizing a liquid raw material. A shutoff valve 112 and a conductance valve 113 are disposed downstream of a suction port 111 provided in the deposition chamber 110. Further, a turbo-molecular pump 120 and a roughing vacuum pump 120a as vacuum pumps are disposed downstream of the conductance valve 113. A substrate holding section (susceptor) 114 for holding a substrate W is provided in the deposition chamber 110. A gas ejection head (shower head) 115 as a gas ejection portion for ejecting a deposition gas toward the substrate W is provided on the upper portion of the deposition chamber 110. An oxidizing gas pipe 130 for supplying an oxidizing gas such as oxygen is connected to the deposition chamber 110.
In such a substrate processing apparatus, a substrate W to be processed is placed on the substrate holding section 114 with the use of a robot hand or the like, and the deposition chamber 110 is evacuated by the vacuum pumps 120, 120a. Then, a lifting/lowering mechanism (not shown) connected to the substrate holding section 114 is driven to lift the substrate holding section 114 to a position for film deposition. A raw material gas mixed with an oxidizing gas is ejected from nozzle holes formed in the gas ejection head 115 toward the substrate W while the substrate W is kept at a predetermined temperature by a temperature adjustment mechanism (not shown). The ejected gases of the raw material gas and the reactive gas are reacted with each other on the surface of the substrate W to form a film thereon. The reacted gas is discharged through the suction port 111 by the vacuum pumps 120, 120a. In some cases, the film deposition is performed while the substrate W on the substrate holding section 114 is being rotated by a rotation mechanism (not shown).
The pressure in the deposition chamber 110 is controlled by adjusting the degree of opening of the shutoff valve 112 and the conductance valve 113 connected to the suction port 111, and by adjusting the amount of gas ejected from the gas ejection head 115. When one of the vacuum pumps 120, 120a is replaced with new one, the shutoff valve 112 is closed to keep the interior of the deposition chamber 110 under vacuum. On the other hand, when a plurality of vacuum pumps 120, 120a are disposed in the system, a shutoff valve disposed upstream of a vacuum pump that is not operated is closed.
In order to efficiently process the substrate, it is necessary to optimize the positional relationship between the substrate and the components in the apparatus or between the substrate and a vacuum pump (vacuum evacuation section). Particularly, this positional relationship should preferably be designed such that the gas introduced from the gas ejection portion is evenly ejected onto the whole surface of the substrate.
Further, in order to improve productivity of processing a substrate and to increase the substrate processing level (fineness), it is necessary to improve the responsiveness in the pressure control in the case where the pressure in the chamber is controlled from an initial pressure to a predetermined pressure. Specifically, it is necessary to dispose the gas ejection portion at a proper position relative to the surface of the substrate for speedily introducing and discharging the gas and improving the controllability of the pressure around the surface of the substrate.
Further, the vacuum pump (vacuum evacuation section) such as a turbo-molecular pump, the shutoff valve and the conductance valve for adjusting the pressure in the chamber, the gas ejection portion, and the like are provided in the conventional substrate processing apparatus, independently of each other. Therefore, spaces for each of these components are required, thereby increasing the size of the apparatus and the vacuum chamber.
The present invention has been made in view of the above drawbacks. It is therefore an object of the present invention to provide a substrate processing apparatus which can optimize a positional relationship between a substrate to be processed and a gas ejection portion or between the substrate and a vacuum evacuation section to improve the responsiveness in a pressure control around the surface of the substrate, and can be downsized.
In order to attain the above object, according to an aspect of the present invention, there is provided a substrate processing apparatus for processing a substrate introduced into a chamber under a low pressure, the substrate processing apparatus comprising: a vacuum pump for evacuating the chamber, the vacuum pump being disposed in the vicinity of the chamber; and a gas ejection portion provided in the vacuum pump for ejecting a gas toward the substrate.
According to another aspect of the present invention, there is provided a substrate processing apparatus for processing a substrate introduced into a chamber under a low pressure, the substrate processing apparatus comprising: a vacuum pump for evacuating the chamber, the vacuum pump being disposed inside of the chamber; and a gas ejection portion provided in the vacuum pump for ejecting a gas toward the substrate.
With this structure, a vacuum pump for evacuating the chamber is provided integrally with a gas ejection portion for ejecting a gas toward the substrate. Accordingly, both of evacuation of a gas from the surface of the substrate and ejection of a gas onto the surface of the substrate can directly be performed, so that the pressure around the surface of the substrate can speedily be adjusted. Therefore, the productivity and quality of processing a substrate can be improved.
When the gas ejection portion in the vacuum pump is provided on a suction side of the vacuum pump, the gas can efficiently be introduced into the chamber while the exhaust capacity of the vacuum pump is sufficiently maintained. Particularly, in the case of a turbo-molecular pump having a rotating exhaust section and a stationary exhaust section which are concentrically provided, no exhaust capacity can be obtained on a rotating shaft of a rotor, i.e., at positions inside of the inner circumferential portion of rotary vanes. Therefore, when the gas ejection portion and a path necessary for the gas ejection portion are provided along the axial direction of the rotating shaft, the gas can efficiently be introduced into the chamber without lowering the exhaust capacity of the pump. Further, since the suction port of the vacuum pump has a less complicate structure than the interior of the vacuum pump, it is easy to provide the gas ejection portion and the path necessary for the gas ejection portion, on the suction port.
According to a preferred aspect of the present invention, the substrate processing apparatus further comprises a gas introduction path passed through at least a portion of a rotor in the vacuum pump for introducing the gas into the gas ejection portion. When the gas introduction path is formed in (a rotating shaft of) the rotor, the gas can be introduced without lowering the exhaust capacity of the pump, and a gas inlet port can be provided at a position opposite to the suction port. This can eliminate the need to provide the gas introduction path and the gas inlet port in the horizontal direction (radial direction) of the vacuum pump. Therefore, a space for installation of the apparatus can be reduced, and the operation of the apparatus can be simplified.
Particularly, when the gas introduction path is linearly formed along the axial direction of the rotating shaft of the rotor, factors of deterioration in the control responsiveness, such as a bend of the gas introduction path, can be eliminated to improve the responsiveness in the pressure control. Consequently, the pressure in the chamber can be controlled without using the shutoff valve or the conductance valve by simply adjusting the amount of gas introduced.
According to another preferred aspect of the present invention, the gas ejection portion in the vacuum pump comprises a valve body for closing and opening a suction port provided on a chamber side of the vacuum pump; and the vacuum pump has a moving mechanism for vertically moving the valve body. Specifically, the vacuum pump also serves as a valve.
With this structure, the pressure in the chamber can efficiently and speedily be controlled by not only adjusting the amount of gas introduced from the gas ejection portion, but also adjusting the degree of opening of the valve body.
As described above, when the gas ejection portion and the gas introduction path are provided in the vacuum pump, a deposition gas can be ejected at an optimal position toward the substrate. Further, contradictory effects, i.e., evacuation of a gas from the surface of the substrate and ejection of a gas onto the surface of the substrate, can simultaneously be obtained.
The above and other objects, features, and advantages of the present invention will be apparent from the following description when taken in conjunction with the accompanying drawings which illustrates preferred embodiments of the present invention by way of example.